Add tests

Author: 0xTim

Tests/SwiftSyntaxMacroExpansionTest/AccessorMacroTests.swift

@@ -25,7 +25,7 @@ import SwiftSyntaxMacros
 import SwiftSyntaxMacrosTestSupport
 import XCTest
 
-private struct ConstantOneGetter: AccessorMacro {
+struct ConstantOneGetter: AccessorMacro {
   static func expansion(
     of node: AttributeSyntax,
     providingAccessorsOf declaration: some DeclSyntaxProtocol,

Tests/SwiftSyntaxMacroExpansionTest/SwiftTestingTests.swift

@@ -0,0 +1,49 @@
+#if canImport(Testing)
+import Testing
+import SwiftSyntaxMacrosTestSupport
+
+@Suite("Swift Testing Macro Expansion Tests")
+struct SwiftTestingMacroExpansionTests {
+  @Test("Test Happy Path")
+  func testHappyPathWorks() {
+    assertMacroExpansion(
+      """
+      @constantOne
+      var x: Int /*1*/ // hello
+      """,
+      expandedSource: """
+        var x: Int { /*1*/ // hello
+          get {
+            return 1
+          }
+        }
+        """,
+      macros: ["constantOne": ConstantOneGetter.self],
+      indentationWidth: .spaces(2)
+    )
+  }
+
+  @Test("Test Failure")
+  func failureReportedCorrectly() {
+    withKnownIssue {
+      assertMacroExpansion(
+        """
+        @constantOne
+        var x: Int /*1*/ // hello
+        """,
+        expandedSource: """
+          var x: Int { /*1*/ // hello
+            get {
+              return 1
+            }
+          }
+          """,
+        macros: ["constantOne": ConstantOneGetter.self],
+        indentationWidth: .spaces(4)
+      )
+    } matching: { issue in
+      issue.description.contains("Macro expansion did not produce the expected expanded source")
+    }
+  }
+}
+#endif